Substituted dihydropyridines are known to be useful for reducing blood pressure, effecting dilation of the coronary vessels, and preventing vasospasms. Typical of such substituted dihydropyridines are those disclosed in U.S. Pat. Nos. 3,923,818; 3,905,970; 4,044,141; 4,237,137; and, 4,285,955. The substituted dihydropyridines disclosed in these patents do not include bridged ring structures.
Weller et al. [J. Org. Chem, 48, 3061-67 (1983)] disclose fused ring and bridged ring structures (e.g., spiro piperidines, spiro pyridines) but indicate that in such structures no exceptionally active analgesics have been found. Furthermore, the bridge portion in these structures is from the ortho position of the benzene ring to the para position of the piperidine or pyridine rings.